Exploitable Yield Gap Research Articles

Yield gap analysis for rainfed grain sorghum in Kansas

AbstractIn the United States, grain sorghum [Sorghum bicolor (L.) Moench] production is concentrated in the US Great Plains region, with the state of Kansas accounting for ∼50% of the planted area. In Kansas, state‐level grain yields steadily increased at a rate of 0.07 Mg ha−1 year−1 from 1957 to 1990. However, since 1990, sorghum yield trends across the United States and Kansas have been exhibiting signs of yield stagnation. The objectives of this study were to (1) quantify the magnitude of the yield gap and (2) identify possible reasons for yield stagnation of rainfed sorghum in Kansas. Current yield (Yc) was estimated as the average yield of the most recently reported 10 years. Maximum attainable yield (Ya) and water‐limited potential yield (Yw) were estimated with a frontier yield function using an extensive dataset of crop performance trials, yield contest data, and county‐level survey yield data totaling 2997 site‐years. State‐level Yc was 4.7 Mg ha−1, which represents 77% of Ya and 49% of Yw. At a regional level, there is a trend of increasing yield gap in central and western Kansas sorghum‐producing regions. Sorghum yield in Kansas appears to be stagnant due to a small exploitable yield gap relative to Ya rather than Yw, a statewide shift in planting area to environments more vulnerable to water deficits, and cultivation in soils with moderate to severe limitations.

Intensifying rice production to reduce imports and land conversion in Africa

Africa produces around 60% of the rice the continent consumes, relying heavily on rice imports to fulfill the rest of the domestic demand. Over the past 10 years, the rice-agricultural area increased nearly 40%, while average yield remained stagnant. Here we used a process-based crop simulation modelling approach combined with local weather, soil, and management datasets to evaluate the potential to increase rice production on existing cropland area in Africa and assess cropland expansion and rice imports by year 2050 for different scenarios of yield intensification. We find that Africa can avoid further increases in rice imports, and even reduce them, through a combination of cropland expansion following the historical trend together with closure of the current exploitable yield gap by half or more. Without substantial increase in rice yields, meeting future rice demand will require larger rice imports and/or land conversion than now.

Mid-season adjustment of nitrogen fertilizer for rice with two plant spacings

ContextFertilizer recommendations for rice (Oryza sativa L.) in Asia often split a predetermined amount of N into several applications to match N supply with anticipated crop demand for N. Within-season deviations from anticipated N demand could necessitate mid-season adjustments in N applications to ensure closure of exploitable yield gaps. ObjectiveWe hypothesized that application of additional fertilizer N to satisfy an underestimated crop demand for N could be delayed until two weeks after panicle initiation without a yield penalty. We additionally examined whether effects of mid-season N adjustments on rice differed between two plant spacings with different plant populations. MethodsField experiments with irrigated, transplanted rice were conducted at two sites in two seasons in North Sumatra, Indonesia. The experimental design was a factorial combination of two rice cultivars, two plant spacings, and seven N treatments. ResultsRice growth and yield components sometimes differed between equally spaced rows (square planting) and alternating narrow and wide rows (legowo), but grain yield with legowo consistently matched and sometimes exceeded yield with square planting. Effects of N treatments — with varying rates and split applications of N — on yield were comparable across the two plant spacings and two cultivars. A predetermined fertilizer recommendation with three split applications of N underestimated the N needed for high yield in all experiments. Application of 30 kg ha−1 more N than the recommended 155 kg ha−1 in dry season (DS) and 125 kg ha−1 in wet season (WS) increased yield by up to 0.5 Mg ha−1 in DS and 0.7 Mg ha−1 in WS and consistently increased net income in both seasons. Additional N at tillering in DS increased vegetative biomass but not yield. Additional N in both seasons could be delayed until 12–14 days after panicle initiation for highest yield. ConclusionsOur study represented circumstances where a fertilizer recommendation provided to farmers before a growing season merited an upward mid-season adjustment in N rate to achieve higher yield. The upward mid-season N adjustment of 30 kg ha−1 in our study could be delayed until two weeks after panicle initiation with no yield penalty in both seasons, for both cultivars, and for both equally spaced rows and alternating narrow and wide rows of transplanted rice. ImplicationsFarmers and advisory services using crop and/or weather monitoring to identify fields meriting additional mid-season N can delay the application of additional N until panicle initiation or two weeks after panicle initiation.

Narrowing the Yield Gap of Coconut (Cocos Nucifera L.) Through Integrated Nutrient Management in the Philippines: An On-Farm Experiment Approach

Over the years, coconut farmers are facing an inherent problem of low productivity in the Philippines due to the senile palms, poor agronomic practices, and other environmental factors. Fertilizer application is not typically practiced in most coconut plantations resulting in yield gaps of 31 to 87% between farmers’ fields and well-managed farms. We aimed to show the potential of integrated nutrient management (INM) in improving coconut productivity and narrowing the yield gap. In this study, five fertilizer treatments viz. T1 - farmer’s practice, T2 - 100% Philippine Coconut Authority’s recommended fertilizer rate (RFR) at two equal splits, applied semi-annually, T3 - 100% RFR at four equal splits, applied quarterly, T4 - 1/2 RFR at two equal splits, applied semi-annually plus one-time application of MykoVAM™, and T5 - 1/2 RFR at four equal splits, applied quarterly plus one-time application of MykoVAM™ were tested in four provinces to represent the four climate conditions in the Philippines. Each experimental site was carried out in a randomized complete block design with three replications. Nut yields from the on-farm experiments were used to analyze the different yield levels and yield gaps. The actual yields were lower than the attainable yields across all the locations. In terms of nut yield, Northern Samar had the highest yield gap of 68%, while Zamboanga City had the lowest yield gap with 21% difference. The exploitable yield gaps were 8,113, 9,408, 2,649 and 3,203 nuts/ha in Palawan, Northern Samar, Zamboanga City and Davao City, respectively. Results suggested that the indigenous soil nutrient content in the farmer’s field was not sufficient to supply the nutrient requirement of the crop compared to the attainable yield. INM has a potential in improving the nut yield. Thus, nutrient management plays a key role in closing the yield gap and in achieving high productivity.

Sustainable improvement strategies for summer maize yield, nitrogen use efficiency and greenhouse gas emission intensity in the North China Plain

In the North China Plain (NCP), the deployment of sub-optimal crop management methods has resulted in low maize grain yields and significant environmental costs arising from a low N partial factor productivity (NPFP) and a rampant greenhouse gas emission intensity (GHGi). We hypothesize that in-situ analysis of the grain yield, NPFP and GHGi at local farms might contribute to improving the crop yield, as well as the environmental sustainability of maize production systems. In this study, we investigated the maize production systems deployed at 1574 local farms in the NCP, and quantified the total yield gap (defined as the difference between the yield potential as simulated by the DSSAT-CERES-Maize model and the actual yield achieved by farmers) and the exploitable yield gap (defined as the difference between the attainable yield as calculated by using the Boundary Line Function (BLF) analysis and the average actual yield achieved by farmers). By combining the results from crop modelling, farmer survey data, and on-farm trials, we were able to identify the dominant factors driving the variability in summer maize yield, NPFP, and GHGi. The results revealed that the average grain yield for summer maize in the NCP was 8.3 t ha−1, and that the total and exploitable yield gaps were 4.9 t ha−1 and 3.0 t ha−1, respectively. The average NPFP was 41 kg kg−1, which amounts to 54% of the attainable NPFP. The average GHGi was 463 kg CO2 eq t−1 grain, which constitutes an increase of 119% over the attainable GHGi. The main factors driving yield include the harvest date and the planting density, and the main factors driving NPFP and GHGi include the N, P and K fertilization rate, where it should be noted that these factors exhibit regional differences. After testing our optimized integrated agronomic management measures in the field experiments, we could confirm that it is possible to narrow the yield gap by 2.7 t ha−1, increase NPFP by 38%, and reduce GHGi by 28%. Obviously, optimizing integrated agronomic management has a great potential for narrowing the yield gap and improving the sustainability of agricultural production.

A sustainable approach to narrowing the summer maize yield gap experienced by smallholders in the North China Plain

CONTEXTThe maize production sector in the North China Plain (NCP) is facing the dual pressures of having to increase its grain yield and improve its environmental sustainability. Evaluating the yield gap and ascertaining the factors that limit the grain yield might suggest new approaches to address these challenges. OBJECTIVEThe objective of this study was to estimate the yield potential and the yield gap associated with smallholdings in the NCP using a hybrid method; to determine the factors driving the grain yield and corresponding sustainability indicators; and to evaluate to what degree the introduction of scientifically developed high-yield and high-efficiency agronomic practices (HH) to smallholders might help to sustainably narrow the exploitable yield gap. METHODSCombined with diagnostic smallholder survey and crop modeling exercise to characterize and decompose yield gaps. With survey data, we assessed the existing variation with respect to various key performance indicators and carried out a number of controlled comparative experiments at farms (HH vs traditional farming practices (FP)) in multiple locations. RESULTS AND CONCLUSIONSOur work revealed the total and exploitable yield gap were 4.3 t ha−1 and 1.8 t ha−1 for rainfed summer maize, and 4.4 t ha−1 and 1.9 t ha−1 for irrigated summer maize across the entire NCP, indicating a large potential for yield improvements. The main factors driving the yield from the entire region were the planting density, the fertilization frequency, and the irrigation frequency. It should be noted that farmers whose yield was in the top 25% bracket of the yield distribution also achieved relatively high utilization efficiencies with respect to N, P, and K fertilizers (15%, 16%, and 16% above the average values, respectively) while their profit was 41% above average. Comparative experiments conducted over several seasons support insights from surveys by demonstrating that major gains in grain yield (+30%), the fertilizer utilization efficiency (+37% in N partial factor productivity, +48% in P partial factor productivity, and + 32% in K partial factor productivity) and economic profit (+62%) are achievable through the adoption of HH. SIGNIFICANCEThrough a hybrid method, our results suggest that agricultural intensification can be achieved in the NCP without having to trade off yield against environmental sustainability. Evidently, smallholders can simultaneously improve their maize grain yield, fertilizer utilization efficiency, and profit by adopting straightforward non-disruptive optimizations of their agronomic practices.

Field validation of a farmer supplied data approach to close soybean yield gaps in the US North Central region

CONTEXTProducer-reported data can be used to identify suites of management practices that lead to higher yield and profit. However, a rigorous field validation of the approach in relation to its potential impact on farmer yield and profit is lacking. OBJECTIVEThis study aimed to validate a producer-data approach on its capability to guide on-farm evaluation of management practices with greatest potential for increasing producer yield and profit. We show proof of concept using soybean in the North Central US region as a case study. METHODSWe used a combination of regression tree analysis and a spatial framework to determine practices with highest influence on yield for specific climate domains across the region. These practices were used as a basis for designing an ‘improved’ management package for each domain. The impact associated with adoption of the ‘improved’ management package on producer yield, seed constituents, and profit was evaluated against a ‘reference’ treatment that follows farmer management via replicated on-farm trials across 100 sites over two crop seasons. RESULTS AND CONCLUSIONSAverage yield was 278 kg ha−1 higher in the improved versus reference management, equivalent to a closure of the current exploitable yield gap by 40%. In turn, adoption of the improved management led to an average increase of $76 ha−1 in net profit. Sensitivity analysis showed that adoption of the improved management packages should increase farmer profit across a wide range of grain price scenarios, with very small downside risk. Seed protein concentration was negatively associated with the positive yield advantage of the improved management, whereas seed oil concentration tended to increase. SIGNIFICANCEAnalysis of producer data can accelerate discovery, evaluation, and adoption of suites of management practices that consistently lead to higher farmer yield and profit, which, in turn, would help speed up current rates of yield gain.

Identifying opportunities to close yield gaps in China by use of certificated cultivars to estimate potential productivity

Even though China has increased grain output in the past decade and greatly contributed to reducing global hunger, the country is still confronted with intense food security pressure due to its huge population base and severe loss of farmland. It has become increasingly important to fully exploit yield gaps (the difference between potential and actual yields) of all staple grains and to identify priority areas in order to achieve the UN sustainable development goal of zero hunger by 2030. The objective of this study was to calculate the production and yield gaps for rice (Oryza sativa L.), wheat (Triticum aestivum L.), and corn (Zea mays L.) across 31 provinces of mainland China, and then to propose sustainable ways to exploit the production and yield gaps in relation to the availability of natural resources and the ecological conditions of the various regions. The yield potential was estimated by assuming that certificated cultivars were adopted in each agricultural ecological zone (AEZ) and that state-of-the-art technologies and best management practices were used. The results suggested that the gross potential productivity of the three staple grains of mainland China in 2016 was 8.86 × 108 tons, with a production gap of 2.99 × 108 tons. Corn exhibited the greatest yield gap. The highest potential productivity was observed in the Northeast Plain and the Huang-Huai-Hai/North China Plain, accounting for 26.35% and 35.91% of the country’s total potential productivity, respectively. The greatest yield gaps were also found in these two plains. To narrow yield gaps, farmland infrastructure, especially irrigation facilities, should be improved, and field management should be strengthened for the provinces with the greatest gaps. However, in view of natural resource constraints (e.g., water shortages in Northern China), water-saving measures and techniques have been encouraged throughout mainland China and the planting of high water-consuming crops such as rice has been discouraged and should be reduced and replaced by other crops in the North China Plain and Northwest China. Using presently available cultivars and field management technologies, China still has great potential to increase grain production and improve food security by closing exploitable yield gaps through the use of suitable production methods based on existing natural resource capacity and ecological status.

Southeast Asia must narrow down the yield gap to continue to be a major rice bowl

Southeast Asia is a major rice-producing region with a high level of internal consumption and accounting for 40% of global rice exports. Limited land resources, climate change and yield stagnation during recent years have once again raised concerns about the capacity of the region to remain as a large net exporter. Here we use a modelling approach to map rice yield gaps and assess production potential and net exports by 2040. We find that the average yield gap represents 48% of the yield potential estimate for the region, but there are substantial differences among countries. Exploitable yield gaps are relatively large in Cambodia, Myanmar, Philippines and Thailand but comparably smaller in Indonesia and Vietnam. Continuation of current yield trends will not allow Indonesia and Philippines to meet their domestic rice demand. In contrast, closing the exploitable yield gap by half would drastically reduce the need for rice imports with an aggregated annual rice surplus of 54 million tons available for export. Our study provides insights for increasing regional production on existing cropland by narrowing existing yield gaps.

Yields and Yield Gaps in Lowland Rice Systems and Options to Improve Smallholder Production

Increasing productivity per unit area, hence closing the yield gap, is key to meeting cereal demand in sub-Saharan Africa. We assessed, with 114 farmers, the contribution of recommended agronomic practices (RAP) with or without NPK fertilization on yield gaps, and options to intensify productivity. Treatments included farmers’ practice (FP) as control, RAP with and without NPK, and farmer-selected best practices geared towards intensification (farmers’ intensification practice, FIP). RAP without fertilization and FIP significantly increased grain yield, each by ca. 12%, whereas RAP+NPK application produced ca. 33% extra yield, over FP. RAP gave the highest mean net income (ca. USD 220 ha−1), fertilizer costs made RAP+NPK gave the lowest mean net income (ca. USD 50 ha−1). Weeding and fertilization timing contributed most to yield variation among fields. Delay in weeding and fertilization created an average yield loss of 5.3 and 1.9 g m−2, per day delay, respectively. Exploitable yield gap averaged 24 and 29%, respectively, across treatments and under FP. RAP, FIP, and RAP+NPK reduced the exploitable yield gap to 25, 26, and 12%, respectively. We conclude that different yield gap levels can be exploited by smallholder farmers in lowland rice systems as RAP, FIP, and RAP+NPK allow yield gap reduction, although fertilization poses a risk to profit at current rice and fertilizer prices. To realize yield gains, farmers with good water management should combine timely weeding with other crop management practices.

Dryland maize yield potentials and constraints: A case study in western Kansas

AbstractWater‐limited environments account for half of the earth's land surface, and dryland agriculture acreage is projected to expand due to climate changes. Examining typical dryland yield potentials and yield improvement measures is crucial for developing future dryland crop production systems. This case study used crop modeling to analyze dryland maize yield potential (YPd), farmers’ yield potential (YPf), and actual farm yields (Ya) from 1990 to 2015 in three counties in western Kansas (i.e., Thomas, Greeley, and Finney in the U.S. Great Plains region). The calibrated APSIM‐Maize model along with actual yields was used to estimate yield gaps attributed to: (a) agronomic factors (YG1 = YPd − YPf) and (b) socioeconomic constraints (YG2 = YPf − Ya). Observed climate conditions during maize‐growing seasons showed warming, brightening, and drying trends for all three counties in western Kansas from 1990 to 2015. Our results showed that the current actual farm yields (Ya) in western Kansas represented only 34%, 32%, and 28% of YPd in Thomas, Greeley, and Finney counties, respectively, indicating significant exploitable yield gaps. Agronomic factors (YG1) contributed the greatest to the yield gap in Greeley and Finney counties, whereas socioeconomic constraints (YG2) offered the greatest opportunity for improvement in Thomas county. Our analysis suggested that improving agronomic management could be a greater priority for further yield improvement in Greeley county, but selecting an appropriate hybrid was a greater priority in Finney county.

Assessing Opportunities to Increase Yield and Profit in Rainfed Lowland Rice Systems in Indonesia

In this study, we aimed to improve rice farmers’ productivity and profitability in rainfed lowlands through appropriate crop and nutrient management by closing the rice yield gap during the dry season in the rainfed lowlands of Indonesia. The Integrated Crop Management package, involving recommended practices (RP) from the Indonesian Agency for Agricultural Research and Development (IAARD), were compared to the farmers’ current practices at ten farmer-participatory demonstration plots across ten provinces of Indonesia in 2019. The farmers’ practices (FP) usually involved using old varieties in their remaining land and following their existing fertilizer management methods. The results indicate that improved varieties and nutrient best management practices in rice production, along with water reservoir infrastructure and information access, contribute to increasing the productivity and profitability of rice farming. The mean rice yield increased significantly with RP compared with FP by 1.9 t ha−1 (ranges between 1.476 to 2.344 t ha−1), and net returns increased, after deducting the cost of fertilizers and machinery used for irrigation supplements, by USD 656 ha−1 (ranges between USD 266.1 to 867.9 ha−1) per crop cycle. This represents an exploitable yield gap of 37%. Disaggregated by the wet climate of western Indonesia and eastern Indonesia’s dry climate, the RP increased rice productivity by 1.8 and 2.0 t ha−1, with an additional net return gain per cycle of USD 600 and 712 ha−1, respectively. These results suggest that there is considerable potential to increase the rice production output from lowland rainfed rice systems by increasing cropping intensity and productivity. Here, we lay out the potential for site-specific variety and nutrient management with appropriate crop and supplemental irrigation as an ICM package, reducing the yield gap and increasing farmers’ yield and income during the dry season in Indonesia’s rainfed-prone areas.

Model-based yield gap analysis and constraints of rainfed sorghum production in Southwest Ethiopia

AbstractFor ensuring food demand of the fast growing population in developing countries, quantification of crop yield gaps and exploring production constraints are very crucial. Sorghum is one of the most important climate change resilient crops in the rainfed farming systems of semi-arid tropics. However, there is little information about yield gaps and production constraints. This study aimed at analysing existing yield gaps and exploring major constraints of sorghum production in Southwest Ethiopia. A crop simulation model approach using AquaCrop and DSSAT was used to estimate potential yield and analyse the yield gaps. Model calibration and evaluation was performed using data from field experiments conducted in 2018 and 2019. Sorghum production constraints were assessed using a survey. The actual and water-limited yield of sorghum ranged from 0.58 to 2.51 and 3.6 to 6.47 t/ha, respectively for the period 2003–17. The regional yield gaps of sorghum for the targeted period were 3.02–3.95 t/ha with a mean value of 3.51 t/ha. Majority of respondent farmers considered seasonal rainfall risk (98%), poor soil fertility (86%), lack of improved varieties (78%) and inadequate weed management (56%) as major factors responsible for the existing yield gaps. The mean exploitable yield gap (2.5 t/ha) between water-limited and actual yield showed the level of existing opportunity for improvement in the actual productivity of sorghum. The gaps also call for introduction of proper interventions such as adoption of improved varieties, planting date adjustment, conservation tillage, fertilizer application and on time weed management.

Rice Yield Gaps in Smallholder Systems of the Kilombero Floodplain in Tanzania

To meet the growing rice demand in Africa, gaps between actual and attainable yields have to be reduced. In Tanzania, this particularly concerns smallholder rain-fed production systems in the floodplains. After quantifying the existing yield gaps, key contributing factors need to be analyzed to improve site-specific management. Field experiments were conducted for three years and in three pedo-hydrological environments (fringe, middle, and center positions) of the Kilombero floodplain to evaluate: (1) The grain yield under farmers’ management (actual yield), (2) yield with the best-recommended management (attainable yield), and (3) the non-limited yield simulated by the APSIM model (potential yield). In the field, we additionally assessed incremental effects of (1) field bunding and soil levelling, (2 and 3) additionally applying of 60 kg N ha−1, as urea or as farmyard manure (FYM), and (4 and 5) incorporating in-situ-grown leguminous green manures. Attainable yields were determined with mineral N application at 120 kg ha−1, additional PK fertilizer and supplemental irrigation. On average across years and positions, the potential, the attainable, and farmers’ actual yields were 11.5, 8.5, and 2.8 t ha−1 indicating a high total yield gap. About 16–38%, 11–20%, and 28–42% of this gap could be attributed to non-controllable yield-reducing (i.e., pest and diseases), yield-limiting (i.e., water and nutrient deficiencies), and yield-defining factors (i.e., poor soil and crop management), respectively. Results indicate a closure of the exploitable yield gap (differences between attainable and farmers’ actual yields) by up to 6.5 t ha−1 (nearly 60% of the potential yield). This exploitable yield gap was larger in 2016 than in 2017. Also, the gap was larger in the water-limited fringe and middle than in the frequently submerged center positions. Simple field bunds combined with land levelling could close 15–35% of the exploitable yield gap, depending on field positions and year. FYM or green manures were less effective than mineral N; however, in 2017 and in the wetter middle and center positions, they reduced the yield gap by >50%. We conclude that yield gaps in rainfed rice in Kilombero floodplain are large, but that a site- and system-specific adaptation of crop management can close much of the exploitable yield gap and increase grain yields by 0.7–4.8 t ha−1. Similar benefits may be obtained in other hydrologically variable floodplain environments of the region and beyond.

Toward a Better Understanding of Genotype × Environment × Management Interactions-A Global Wheat Initiative Agronomic Research Strategy.

The Wheat Initiative (WI) and the WI Expert Working Group (EWG) for Agronomy (www.wheatinitiative.org) were formed with a collective goal to “coordinate global wheat research efforts to increase wheat production, quality, and sustainability to advance food security and safety under changing climate conditions.” The Agronomy EWG is responsive to the WI’s research need, “A knowledge exchange strategy to ensure uptake of innovations on farm and to update scientists on changing field realities.” The Agronomy EWG aims to consolidate global expertise for agronomy with a focus on wheat production systems. The overarching approach is to develop and adopt a systems-agronomy framework relevant to any wheat production system. It first establishes the scale of current yield gaps, identifies defensible benchmarks, and takes a holistic approach to understand and overcome exploitable yield gaps to complement genetic increases in potential yield. New opportunities to increase productivity will be sought by exploiting future Genotype × Environment × Management synergies in different wheat systems. To identify research gaps and opportunities for collaboration among different wheat producing regions, the EWG compiled a comprehensive database of currently funded wheat agronomy research (n = 782) in countries representing a large proportion of the wheat grown in the world. The yield gap analysis and research database positions the EWG to influence priorities for wheat agronomy research in member countries that would facilitate collaborations, minimize duplication, and maximize the global impact on wheat production systems. This paper outlines a vision for a global WI agronomic research strategy and discusses activities to date. The focus of the WI-EWG is to transform the agronomic research approach in wheat cropping systems, which will be applicable to other crop species.

Yield Gap Management under Seawater Intrusion Areas of Indonesia to Improve Rice Productivity and Resilience to Climate Change

The purpose of this study was to evaluate (a) the performance of two modern rice varieties (non-tolerant and tolerant for saline soils) under different fertilizer management options, and (b) assess the yield gap and income increase through proper crop and nutrient management at different levels of soil salinity. Experiments were carried out in moderate and high levels of soil salinity in West Java, Indonesia. A split plot design with three replications was used. The main plots included two rice varieties, Inpari-30 Ciherang sub1 and Inpari-34 (tolerant variety for saline soils), and subplots included eight fertilizer management treatments. Farmer participatory field trials were also established across three levels of soil salinity with four different rice varieties, Sidenuk, Inpari 30, Inpari 34, and Inpari 35, and a fertilizer package consisting of organic and inorganic fertilizers. Under low and moderate soil salinities, Sidenuk and Inpari 30 with recommended practice had higher productivity and economic benefit compared to the saline tolerant rice varieties, Inpari 34 and Inpari 35. However, under high soil salinity, the yields of Inpari 34 and Inpari 35 with recommended practice were 93% higher than farmers’ practice, representing an exploitable yield gap of 1.3 t ha−1 and benefit above fertilizer cost of USD 301 ha−1. The combination of tolerant varieties and improved nutrient management use for rice production can therefore be used as a strategy for improving farmers’ income and livelihoods in coastal areas of Indonesia.

Integrating remote sensing-based process model with environmental zonation scheme to estimate rice yield gap in Northeast China

Yield gap (YG) analysis is a powerful method to reveal the possible opportunities for fulfilling the growing food demand. It used to be restricted to a small geographic area, and thus the scope of untapped yield often remains unclear at macro scale. To this end, this study presents an improved remote sensing approach to assessing regional rice YG in northeast China (NEC) during the period from 2006 to 2017. A satellite-based biophysical model (BEPS) was used to derive the actual yield (Ya) and its spatial patterns. A machine-learning zonation scheme was further developed to estimate the potential yield for farmers (Yp) within domains having similar climatic, geomorphic, and edaphic context. Results indicate that the BEPS model can provide reliable estimates of rice yields in this region, with RMSE below 20 % at the county level; and the novel zonation scheme enables better portrayal of the spatial variation in Yp. To identify areas with the greatest potential to narrow the YG, we proposed a quantitative method for dividing NEC into four parts with different priorities for future yield improvement. In general, the exploitable YG in NEC was 2599 kg ha−1, amounting to 24.7 % of Yp. Southern NEC possessed substantial YG with the primary priority to be explored; whereas in the north, Ya already approximating Yp, further yield increase was limited and challenging. Growing degree days (≥10 °C), cumulative solar radiation and elevation were all significant limiting factors of Yp. This study demonstrates the ability of remote sensing approach to assessing regional YG. Meanwhile, this regional assessment can support planners to set practical yield target and to prioritize regions and needs for future exploitation and researches.

Using fertiliser to maintain soil inorganic nitrogen can increase dryland wheat yield with little environmental cost

Nitrogen (N) deficiency is responsible for a large proportion of the exploitable yield gap that exists in Australian wheat production. In order to maximise N use efficiency (NUE), growers attempt to match N fertiliser to seasonal water limited yield potential, which in the southern grain growing region is largely determined by in-crop rainfall. Australia’s variable rainfall makes water limited yield potential very difficult to predict, and growers tend to under fertilise, fearing economic and environmental losses of N if crops are over-fertilised. However, environmental losses of excess N are low in the semi-arid, winter dominant rainfall environments with high water holding capacity soils that comprise much of the wheat producing regions of south eastern Australia. This is particularly the case when high carbon (C) to N ratio crop residues are retained which facilitate rapid immobilisation of any mineral N surplus to crop requirements. We therefore propose that the exploitable yield gap in wheat could be closed if a longer-term strategy of N fertiliser application was adopted. In this strategy, growers would simply use N fertiliser to maintain an environmentally appropriate base level of inorganic N (N bank) rather than attempting to match fertiliser inputs to seasonal conditions. We used field studies with 15N labelled fertiliser and cropping systems simulations to demonstrate that fertiliser N applied at rates calculated to maintain fixed thresholds of inorganic N (N bank criteria) and top-dressed immediately prior to the period of rapid crop uptake can substantially increase yields and profit in comparison to current practice, even when applications exceed crop demand in some years. A further benefit of this strategy is an increase in soil organic matter. Both field and simulation studies indicate that the environmental cost of such a strategy would be minimal, with only a small increase in leaching and denitrification despite higher overall rates of N application. This strategy needs to be compared with current practices in longer term field experiments to confirm production increases and lack of environmental impacts.

Can potato add to China's food self-sufficiency? The scope for increasing potato production in China

Abstract China is enhancing potato production in both area and quantity. While the potato area is large, the actual yields remain low. Besides, the water resources used for irrigation are increasingly under pressure in potato production areas. This study aimed to assess the scope for increasing potato production in China. The key climate zones in China were identified, for which the potential yield (Yp) and water limited yield (Yw) of potato (expressed in fresh matter (FM)) were estimated by two crop growth models over 10 years (2006–2015). The Yp and Yw and yield gaps (i.e., the difference between Yp and actual yield (Ya) under irrigated conditions (Yg-p) and between Yw and Ya under rainfed conditions (Yg-w)) were evaluated at local, provincial and national level, for potatoes under both irrigated and rainfed conditions. The water availability through rainfall, water productivity (WP) and the water input gaps to realize potential rather than water-limited potato yields were identified at provincial level. The Yp in the country was on average 50.1 ton FM ha−1, and Yg-p as a percentage of Yp was 66%. At provincial level, the Yp varied from 38.8 ton FM ha−1 in Sichuan in the southwest to 66.4 ton FM ha−1 in Qinghai in the north. At national level, the Yw was 43.7 ton FM ha−1 and Yg-w as a percentage of Yw was 61%. At provincial level, the Yw was lowest in Shaanxi (27.7 ton FM ha−1) and highest in Qinghai (57.9 ton FM ha−1). Water productivity for potential yield (WP-p) ranged between 30.7 and 54 kg dry matter (DM) mm−1 ha−1 in Shaanxi and Qinghai, respectively, and for actual yield (WP-a) between 7.9 kg DM mm−1 ha−1 (Shanxi) and 22.3 kg DM mm−1 ha−1 (Sichuan). Water supply through rainfall is close to sufficient for non-water limiting potato growth in the southwest. The water input gap in the north was highest in Shaanxi (i.e., 243 mm) and lowest in Heilongjiang (i.e., 39 mm). There is a large scope to improve potato yields at current rainfall levels, especially in Qinghai and Heilongjiang in the north and in Guizhou in the southwest. By closing the exploitable yield gap (i.e., difference between 80% of Yp - or of Yw - and Ya) for the current production area, potato could contribute to an additional 1.1 and 0.9 1014 kcal, respectively, under irrigated and rainfed conditions. This is much more than that for rice (0.2 1014 kcal extra energy due to yield gap closure) under irrigated conditions, and similar or more than for maize under irrigated (1.0 1014 kcal) and rainfed (0.5 1014 kcal) conditions. We conclude that compared with the cereal staple crops, potato has a larger potential to maintain domestic food security and self-sufficiency, and to enhance water use efficiency.

Yield gap analysis of major pulses in India

In order to assess the nature and extent of yield gap in major pulses in India, published data from different official records were used for different time periods and comparison was made between states and India regarding yield difference of different pulses. Yield gap II was assessed with the help of data obtained from annual reports of Indian Institute of Pulses Research, Kanpur for major pulses crops. Both yield gap I and Yield gap II was examined in case of chickpea for the period of 2011-12 taking an aggregated yield data. The result revealed that most of the major pulses growing states were having lower yield of total pulses than national average while minor states showed higher yield during 2006-2012. With the positive growth in yield of individual pulses minor states were moving forward and showed potential increase in production of pulses. Yield gap II of major pulses in India showed an increase in the recent period over 2006-07. In case of chickpea frontline demonstration data for the period of 2011-12 revealed that yield gap II ranged from 7.63% in Karnataka to 24.37% in Madhya Pradesh among major chickpea producing states while this gap was 15.80% in Chattishgarh and 29.09% in Bihar among minor states. Yield gap for the same period was observed to be 28.46% in Madhya Pradesh, 28.75% in Karnataka and 28.56% in Maharashtra. These states contribute more than 50% of area share indicating tremendous untapped potential. Factors causing exploitable yield gap could be managed with effective implementation of government program along with participatory research and extension services ensured within the time frame.Journal of the Institute of Agriculture and Animal Science.Vol. 33-34, 2015, page: 213-219